1. Field of the Invention
This invention relates to an improved ship's derrick which can be swiveled and tripped up by means of a suitable bearing such as a goose-neck pin-bearing, and one or more topping lift tackles, and whose load tackle is attached to a crab which can be moved, by means of tackle lines, in the derrick's longitudinal direction.
2. Description of the Prior Art
It has been known to hold either the derrick's topping lift rope, together with the swiveling rope or guy rope, in a state of tension by means of the loading weight which is suspended from a crab which travels along the derrick (DE-PS 622 830), or, with horizontal derricks, in the case of a derrick with a height adjustable goose-pin bearing, a load should be shifted horizontally (DE-PS 19 56 215). In both cases, ropes are provided, the tension in which keeps the crab fixed in place or slides it in both directions along the boom.
In spite of these known types of derricks there remains a very real and substantial need for derricks which contribute to improved ship's stability.